package com.xsherl.leetcode.solution;

import com.xsherl.leetcode.utils.ArrayUtils;
import com.xsherl.leetcode.utils.PrintUtils;

public class MinimumPathSum {

    /**
     * 动态规划
     *  dp[i][j] = Math.min(dp[i - 1][j], dp[i][j - 1]) + grid[i][j];
     */
    public int minPathSum(int[][] grid) {
        int m = grid.length, n = grid[0].length;
        int[][] dp = new int[m][n];
        dp[0][0] = grid[0][0];
        for (int i = 1; i < m; ++i){
            dp[i][0] = dp[i - 1][0] + grid[i][0];
        }
        for (int j = 1; j < n; ++j){
            dp[0][j] = dp[0][j - 1] + grid[0][j];
        }
        for (int i = 1; i < m; i++){
            for (int j = 1; j < n; j ++){
                dp[i][j] = Math.min(dp[i - 1][j], dp[i][j - 1]) + grid[i][j];
            }
        }
        return dp[m - 1][n -1];
    }

    /**
     * 优化后的动态规划
     * 使用一维数组来存储每一行从左到右的和，当移动到下一行的时候，dp[i] = Math.min(dp[i], dp[i - 1]) + g[row][i]
     */
    public int minPathSum1(int[][] grid) {
        int m = grid.length, n = grid[0].length;
        int[] dp = new int[n];
        dp[0] = grid[0][0];
        for (int i = 1; i < n; ++i){
            dp[i] = dp[i - 1] + grid[0][i];
            System.out.println(dp[i]);
        }
        PrintUtils.println(dp);
        for (int i = 1; i < m; i++){
            for (int j = 0; j < n; j ++){
                if (j == 0){
                    dp[j] += grid[i][j];
                } else {
                    dp[j] = Math.min(dp[j], dp[j - 1]) + grid[i][j];
                }
            }
            PrintUtils.println(dp);
        }
        return dp[n -1];
    }

    public static void main(String[] args) {
        int[][] ints = ArrayUtils.parseArray("" +
                "[[1,2,3],[4,5,6]]" +
                "", int[].class);
        int i = new MinimumPathSum().minPathSum1(ints);
        System.out.println(i);
    }
}
